/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.propertyeditors;

import java.beans.PropertyEditorSupport;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;

/**
 * Property editor for Maps, converting any source Map
 * to a given target Map type.
 *
 * @author Juergen Hoeller
 * @see java.util.Map
 * @see java.util.SortedMap
 * @since 2.0.1
 */
public class CustomMapEditor extends PropertyEditorSupport {

    @SuppressWarnings("rawtypes")
    private final Class<? extends Map> mapType;

    private final boolean nullAsEmptyMap;


    /**
     * Create a new CustomMapEditor for the given target type,
     * keeping an incoming {@code null} as-is.
     *
     * @param mapType the target type, which needs to be a
     * sub-interface of Map or a concrete Map class
     * @see java.util.Map
     * @see java.util.HashMap
     * @see java.util.TreeMap
     * @see java.util.LinkedHashMap
     */
    @SuppressWarnings("rawtypes")
    public CustomMapEditor(Class<? extends Map> mapType) {
        this(mapType, false);
    }

    /**
     * Create a new CustomMapEditor for the given target type.
     * <p>If the incoming value is of the given type, it will be used as-is.
     * If it is a different Map type or an array, it will be converted
     * to a default implementation of the given Map type.
     * If the value is anything else, a target Map with that single
     * value will be created.
     * <p>The default Map implementations are: TreeMap for SortedMap,
     * and LinkedHashMap for Map.
     *
     * @param mapType the target type, which needs to be a
     * sub-interface of Map or a concrete Map class
     * @param nullAsEmptyMap ap whether to convert an incoming {@code null}
     * value to an empty Map (of the appropriate type)
     * @see java.util.Map
     * @see java.util.TreeMap
     * @see java.util.LinkedHashMap
     */
    @SuppressWarnings("rawtypes")
    public CustomMapEditor(Class<? extends Map> mapType, boolean nullAsEmptyMap) {
        Assert.notNull(mapType, "Map type is required");
        if (!Map.class.isAssignableFrom(mapType)) {
            throw new IllegalArgumentException(
                    "Map type [" + mapType.getName() + "] does not implement [java.util.Map]");
        }
        this.mapType = mapType;
        this.nullAsEmptyMap = nullAsEmptyMap;
    }

    /**
     * Convert the given value to a Map of the target type.
     */
    @Override
    public void setValue(@Nullable Object value) {
        if (value == null && this.nullAsEmptyMap) {
            super.setValue(createMap(this.mapType, 0));
        } else if (value == null || (this.mapType.isInstance(value) && !alwaysCreateNewMap())) {
            // Use the source value as-is, as it matches the target type.
            super.setValue(value);
        } else if (value instanceof Map) {
            // Convert Map elements.
            Map<?, ?> source = (Map<?, ?>) value;
            Map<Object, Object> target = createMap(this.mapType, source.size());
            source.forEach((key, val) -> target.put(convertKey(key), convertValue(val)));
            super.setValue(target);
        } else {
            throw new IllegalArgumentException("Value cannot be converted to Map: " + value);
        }
    }

    /**
     * Create a Map of the given type, with the given
     * initial capacity (if supported by the Map type).
     *
     * @param mapType a sub-interface of Map
     * @param initialCapacity the initial capacity
     * @return the new Map instance
     */
    @SuppressWarnings({"rawtypes", "unchecked"})
    protected Map<Object, Object> createMap(Class<? extends Map> mapType, int initialCapacity) {
        if (!mapType.isInterface()) {
            try {
                return ReflectionUtils.accessibleConstructor(mapType).newInstance();
            } catch (Throwable ex) {
                throw new IllegalArgumentException(
                        "Could not instantiate map class: " + mapType.getName(), ex);
            }
        } else if (SortedMap.class == mapType) {
            return new TreeMap<>();
        } else {
            return new LinkedHashMap<>(initialCapacity);
        }
    }

    /**
     * Return whether to always create a new Map,
     * even if the type of the passed-in Map already matches.
     * <p>Default is "false"; can be overridden to enforce creation of a
     * new Map, for example to convert elements in any case.
     *
     * @see #convertKey
     * @see #convertValue
     */
    protected boolean alwaysCreateNewMap() {
        return false;
    }

    /**
     * Hook to convert each encountered Map key.
     * The default implementation simply returns the passed-in key as-is.
     * <p>Can be overridden to perform conversion of certain keys,
     * for example from String to Integer.
     * <p>Only called if actually creating a new Map!
     * This is by default not the case if the type of the passed-in Map
     * already matches. Override {@link #alwaysCreateNewMap()} to
     * enforce creating a new Map in every case.
     *
     * @param key the source key
     * @return the key to be used in the target Map
     * @see #alwaysCreateNewMap
     */
    protected Object convertKey(Object key) {
        return key;
    }

    /**
     * Hook to convert each encountered Map value.
     * The default implementation simply returns the passed-in value as-is.
     * <p>Can be overridden to perform conversion of certain values,
     * for example from String to Integer.
     * <p>Only called if actually creating a new Map!
     * This is by default not the case if the type of the passed-in Map
     * already matches. Override {@link #alwaysCreateNewMap()} to
     * enforce creating a new Map in every case.
     *
     * @param value the source value
     * @return the value to be used in the target Map
     * @see #alwaysCreateNewMap
     */
    protected Object convertValue(Object value) {
        return value;
    }

    /**
     * This implementation returns {@code null} to indicate that
     * there is no appropriate text representation.
     */
    @Override
    @Nullable
    public String getAsText() {
        return null;
    }

    /**
     * Convert the given text value to a Map with a single element.
     */
    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        setValue(text);
    }

}
